A standard profiled construction element comprises inner and outer metallic, normally aluminum, profiles that extend parallel to each other and that are bridged by a pair of webs, often formed of plastic. The outer metal profile is exposed to the elements on the outside of the building and the inside profile is turned to the interior, with the two plastic webs forming a thermal bridge between them. Inner faces of the profiles and of the webs define a longitudinally extending and transversely closed passage.
In order to increase the insulating capacity of such a structure, to make it mechanically more rigid, and to prevent convection currents inside it, it is known from German patent documents 94 22 032 and 100 39 980 and from EP 0,978,619 and EP 1,318,262 to substantially completely fill this space with an insulating body, normally a closed-cell rigid plastic foam. It is also known from German 94 13 790 and EP 0,636,760 to provide such a foam body having oppositely directed broad outer faces bonded in surface contact to inner faces of opposing inner walls of the element.
Such structures have the disadvantage that when they are exposed to substantial heat, the plastic body can expand and deform the plastic webs. This can particularly occur at the high temperatures of certain lacquering operations. Furthermore manufacture of them is fairly difficult as the plastic insulating body must normally be formed in situ in the finished four-part structure.
Another system described in German 196 22 278 has a pair of bars of insulating material fixed to inner faces of the two bridging webs. These bars do not contact anything other than the web they are fixed to. They serve mainly to interfere with convective flow in the structure. Overall they offer poor insulating performance and do not prevent deformation of the structure.